About the Author

Ambrogio Damiano Achille Ratti, later Pope Pius XI (1857 – 1939) became pope in 1922. This meant Pius XI would oversee the response to the outbreak of the persecution of Catholics in the new Soviet Union, then in Mexico in the outbreak of the Cristero War, and finally in Spain in the lead up to the Spanish Civil War. In many respects, Pope Pius XI looked to Leo XIII for inspiration, including to his predecessor’s treatment of marriage in Arcanum Divinae. Pope Pius XI wrote Casti Conubii in 1930. The text is simplified, with no notes except for scripture references. The full text with the notes is available on the Vatican website.

Pope Pius XI on the role of the will in entering into marriage

Yet although matrimony is of its very nature of divine institution, the human will, too, enters into it and performs a most noble part. For each individual marriage, inasmuch as it is a conjugal union of a particular man and woman, arises only from the free consent of each of the spouses; and this free act of the will, by which each party hands over and accepts those rights proper to the state of marriage, is so necessary to constitute true marriage that it cannot be supplied by any human power. This freedom, however, regards only the question whether the contracting parties really wish to enter upon matrimony or to marry this particular person; but the nature of matrimony is entirely independent of the free will of man, so that if one has once contracted matrimony he is thereby subject to its divinely made laws and its essential properties. For the Angelic Doctor [that is, Saint Thomas Aquinas], writing on conjugal honor and on the offspring which is the fruit of marriage, says: “These things are so contained in matrimony by the marriage pact itself that, if anything to the contrary were expressed in the consent which makes the marriage, it would not be a true marriage.” 

By matrimony, therefore, the souls of the contracting parties are joined and knit together more directly and more intimately than are their bodies, and that not by any passing affection of sense of spirit, but by a deliberate and firm act of the will; and from this union of souls by God’s decree, a sacred and inviolable bond arises. Hence the nature of this contract, which is proper and peculiar to it alone, makes it entirely different both from the union of animals entered into by the blind instinct of nature alone in which neither reason nor free will plays a part, and also from the haphazard unions of men, which are far removed from all true and honorable unions of will and enjoy none of the rights of family life.

From this it is clear that legitimately constituted authority has the right and therefore the duty to restrict, to prevent, and to punish those base unions which are opposed to reason and to nature; but since it is a matter which flows from human nature itself, no less certain is the teaching of Our predecessor, Leo XIII of happy memory: “In choosing a state of life there is no doubt but that it is in the power and discretion of each one to prefer one or the other: either to embrace the counsel of virginity given by Jesus Christ, or to bind himself in the bonds of matrimony. To take away from man the natural and primeval right of marriage, to circumscribe in any way the principal ends of marriage laid down in the beginning by God Himself in the words ‘Increase and multiply’ (Genesis 1:28), is beyond the power of any human law.”

Therefore the sacred partnership of true marriage is constituted both by the will of God and the will of man. From God comes the very institution of marriage, the ends for which it was instituted, the laws that govern it, the blessings that flow from it; while man, through generous surrender of his own person made to another for the whole span of life, becomes, with the help and cooperation of God, the author of each particular marriage, with the duties and blessings annexed thereto from divine institution.